var watchExampleVM = new Vue({
    el: '#watch-example',
    data: {
        question: '',
        answer: 'I cannot give you an answer until you ask a question!'
    },
    watch: {
        // 如果 `question` 发生改变，这个函数就会运行
        question: function (newQuestion, oldQuestion) {
        this.answer = 'Waiting for you to stop typing...'
        this.debouncedGetAnswer()
        }
    },
    created: function () {
        // `_.debounce` 是一个通过 Lodash 限制操作频率的函数。
        // 在这个例子中，我们希望限制访问 yesno.wtf/api 的频率
        // AJAX 请求直到用户输入完毕才会发出。想要了解更多关于
        // `_.debounce` 函数 (及其近亲 `_.throttle`) 的知识，
        // 请参考：https://lodash.com/docs#debounce
        this.debouncedGetAnswer = _.debounce(this.getAnswer, 500)
    },
    methods: {
        getAnswer: function () {
        if (this.question.indexOf('?') === -1) {
            this.answer = 'Questions usually contain a question mark. ;-)'
            return
        }
        this.answer = 'Thinking...'
        var vm = this
        axios.get('https://yesno.wtf/api')
            .then(function (response) {
            vm.answer = _.capitalize(response.data.answer)
            })
            .catch(function (error) {
            vm.answer = 'Error! Could not reach the API. ' + error
            })
        }
    }
})